Removal of phenanthrene from synthetic kaolin soils by electrokinetic soil flushing

Abstract

In this work, the scale up of the flushing-fluid-assisted electrokinetic remediation of kaolin soil polluted with phenanthrene has been studied. Three different scales have been used: lab (25 cm3), bench (28 × 103 cm3) and pilot scale (175 × 103 cm3) plants. Results show that electrokinetic fluxes, removals of PHE and pollutant distribution in soil were very different in the three setups in spite of being the same soil, pollutant and operation conditions. Electro-osmotic fluxes were much bigger in the case of the lab scale setup and very similar in the bench scale plant and in the pilot mock up, just as expected according to the PHE fluxes and to the distribution of PHE removal. Moreover, in the pilot scale plant used, hydraulic flux produced by gravity and evaporation flux by electric heating of the soil should be taken considered. This variety of results suggests a very complex process with many factors influencing on results. In the lab scale plant, the main mechanisms involved in the removal of PHE are dragging with electro-osmotic flow in the cathodic wells and electrophoresis after interaction of surfactant with phenanthrene in the anodic wells. Just on the contrary, desorption of PHE promoted by the electric heating seems to be a very significant removal mechanism in the bench scale plant and in the pilot mock-up.